The fundamental absorption edge in MnIn2Se4 layer semi-magnetic semiconductor

From the study of the optical absorption coefficient and photoluminescence spectra of the layer semi-magnetic semiconductor MnIn2Se4 the nature of its fundamental absorption edge is established. It is found that the lowest-energy-gap of this compound is allowed-indirect between parabolic bands that vary from about 1.55–1.43 eV in the temperature range from 10 K to room temperature. In addition, two allowed direct band-to-band transitions beginning at 1.72 and 1.85 eV at 295 K, and at 1.82 and 1.96 eV at 10 K which are related to optical absorption processes between the uppermost Γ4(z) and the middle Γ5(x) valence bands and the conduction band respectively, are observed in the high energy range. It is also found that the crystal field splitting parameter (Δcf) of MnIn2Se4 is of about 0.15 eV nearly independent of the temperature. At energies around 2.2 eV a photoluminescence band related to internal transitions between d-excited levels of Mn+2 ion to its 6A1 ground state is also observed in spectra.